LithosAnanake/kernel/include/starkernel/repl.h

/*
  StarForth — Steady-State Virtual Machine Runtime

  Copyright (c) 2023–2025 Robert A. James
  All rights reserved.

  Licensed under the StarForth License, Version 1.0
*/

/**
 * repl.h - Emergency FORTH REPL for LithosAnanke kernel
 */

#ifndef STARKERNEL_REPL_H
#define STARKERNEL_REPL_H

#include "vm.h"
#include "starkernel/homeblocks_sig.h"

struct blkio_dev;

#ifdef __cplusplus
extern "C" {
#endif

/**
 * sk_repl - Run the emergency FORTH REPL on the serial console.
 *
 * Blocks until vm->halted is set (BYE word) or the VM encounters a halt.
 * Runs with interrupts enabled; the APIC heartbeat continues to fire.
 *
 * @param vm  Mama VM instance (must be fully initialised)
 */
void sk_repl(VM *vm);

/**
 * sk_repl_run - Bare REPL loop (no banner).
 *
 * Same as sk_repl but skips the version/welcome banner.  Used by START
 * to enter a child VM's interpreter loop without reprinting the header.
 *
 * @param vm  Fully initialised VM instance
 */
void sk_repl_run(VM *vm);

/**
 * sk_repl_step - Execute one REPL turn on a VM and return.
 *
 * Prints the VM's prompt, reads one line, interprets it, prints ok/ERROR,
 * then returns.  Used by the Compudynamics VM-STEP primitive so Hera can
 * give a single REPL quantum to a child VM without surrendering control
 * for the full sk_repl_run() loop.
 *
 * @param vm  Fully initialised VM instance
 * @return 1 if the VM is still running, 0 if it halted during this turn
 */
int sk_repl_step(VM *vm);

/**
 * sk_repl_set_active_vm - Redirect REPL input to a different VM (USE word).
 *
 * Pass NULL to restore default dispatch (Mama's VM).
 * The change takes effect on the next REPL iteration.
 *
 * @param vm  Target VM, or NULL for default
 */
void sk_repl_set_active_vm(VM *vm);

/**
 * sk_repl_get_active_vm - Return the current USE-redirected VM, or NULL.
 */
VM *sk_repl_get_active_vm(void);

/**
 * sk_repl_get_homeblocks_dev / sk_repl_get_homeblocks_sig - The currently
 * attached home-blocks USB drive, or NULL if none is attached / the
 * attached drive didn't check out as HOMEBLOCKS_SIG_OK (FABRIC-2.md
 * §F.6/§F.9/§F.18). Both return NULL together; never one without the
 * other.
 */
struct blkio_dev *sk_repl_get_homeblocks_dev(void);
const homeblocks_sig_t *sk_repl_get_homeblocks_sig(void);

/**
 * sk_repl_get_attached_blk_dev - The currently attached USB block
 * device, regardless of home-blocks recognition (FABRIC-2.md
 * §F.8/§F.19) -- MINT's own target, since a blank/unminted drive never
 * sets sk_repl_get_homeblocks_dev() above. NULL if nothing is attached.
 */
struct blkio_dev *sk_repl_get_attached_blk_dev(void);

/**
 * sk_repl_register_words - Registers repl.c's own FORTH-visible words
 * (currently just BLK-ATTACH-ACK, Artemis's storage-attach reply target --
 * see sk_word_blk_attach_ack()'s doc comment in repl.c). Call once from
 * register_forth79_words() alongside the other __STARKERNEL__-only
 * registration calls.
 */
void sk_repl_register_words(VM *vm);

/**
 * sk_console_getkey - Real body of the standard dictionary's KEY word
 * (called from shim.c's getchar()). Blocks until a key is available from
 * either input source (serial console or the PS2/virtio keyboard-event
 * bridge), servicing the heartbeat/idle loop while waiting so a KEY call
 * from inside any word never stalls the heartbeat. No echo -- that's the
 * caller's responsibility, same as any standard KEY.
 *
 * @param active_vm  VM whose idle dispatch runs while waiting (see
 *                   sk_repl_idle()'s own doc comment on why this is a
 *                   parameter rather than read via sk_repl_get_active_vm())
 * @return the key read, as an unsigned byte value
 */
int sk_console_getkey(VM *active_vm);

/**
 * sk_console_key_available - Real body of the standard dictionary's
 * ?TERMINAL word (called from sf_terminal_ready()). Non-blocking peek:
 * returns 1 if a key is ready without consuming it (a following
 * sk_console_getkey() returns that exact key), 0 otherwise.
 */
int sk_console_key_available(void);

/**
 * sk_console_readline - Real body of the standard dictionary's
 * QUERY/EXPECT words (called from shim.c's fgets()). Reads one line from
 * the console with echo and backspace support, servicing the heartbeat/
 * idle loop while waiting -- the same line editor the REPL's own prompt
 * uses internally, so a mid-word EXPECT behaves identically to typing at
 * "ok>" itself.
 *
 * @param buf            Destination buffer
 * @param size           Buffer capacity, including the NUL terminator
 * @param active_vm      VM whose idle dispatch runs while waiting
 * @param reanchor_prompt  Nonzero to re-print the "ok> " prompt whenever
 *                an idle bottom half (heartbeat, USB attach/detach) writes
 *                to the console while this readline blocks at a bare,
 *                untyped prompt -- keeps the top-level prompt as the last
 *                thing shown once the chatter dies down. Callers whose
 *                prompt line is their own (shim.c's fgets(), i.e.
 *                QUERY/EXPECT/ACCEPT) pass 0 so "ok> " never gets stamped
 *                onto their mid-word input context.
 * @return number of characters placed in buf, not counting the NUL, or -1
 *         (2026-09-06) when reanchor_prompt is nonzero and the attached
 *         identity logged out while this call was blocked waiting for
 *         input with nothing typed yet -- see repl.c's own doc comment
 *         on this function for what a caller must do with -1.
 */
int sk_console_readline(char* buf, int size, VM* active_vm, int reanchor_prompt);

/**
 * sk_repl_headless_wait - Idle-service loop with no interactive surface
 * at all: no banner, no prompt, no console_getc()/readline. Runs
 * heartbeat_service() and the same SK_IDLE_BEAT_INTERVAL-gated
 * sk_repl_idle(mama) cadence sk_console_readline()'s own idle branch
 * uses -- so USB/WIREBIND/Zuse-attach detection, the heartbeat, and all
 * other idle-tick subsystems keep running -- until a real identity is
 * currently attached (Zuse's own session, or a WIREBIND user), at which
 * point it returns.
 *
 * Revised 2026-09-06: originally exited on a one-way sticky "has anyone
 * ever logged in this boot" flag (sk_console_mark_login()/sk_console_
 * login_occurred(), both retired) -- that let a real gap through, found
 * live: once the flag tripped once, it never reset, so a later full
 * logout (nobody attached at all) fell through to a bare, unauthenticated
 * prompt instead of going silent again. This now checks live attach
 * state instead (repl.c's own sk_console_identity_present()), and is
 * called from two places: once from kernel_main.c in place of an
 * immediate sk_repl(mama) call when EMERGENCY_CONSOLE_ENABLED is off (the
 * default, 2026-09-05) -- no thumbdrive, no prompt, at boot -- and again
 * from inside sk_repl_run()'s own main loop, every time nobody is
 * currently attached, so the same silence re-engages after any later
 * logout mid-boot too. When EMERGENCY_CONSOLE_ENABLED is on (the debug/
 * recovery escape hatch), neither call site applies -- the console shows
 * immediately and stays visible regardless of attach state, exactly as
 * before this change.
 *
 * @param mama  Hera's own VM instance -- the idle-dispatch target,
 *              same as every other sk_repl_idle() caller uses.
 */
void sk_repl_headless_wait(VM *mama);

#ifdef __cplusplus
}
#endif

#endif /* STARKERNEL_REPL_H */